Elliot Formation
Elliot Formation | |
---|---|
Stratigraphic range: Norian-Pliensbachian ~ | |
![]() Elliot Formation caves in the Matalane Valley, Leribe, Lesotho | |
Type | Geological formation |
Unit of | Stormberg Group |
Sub-units | Upper Elliot, Lower Elliot |
Underlies | Clarens Formation |
Overlies | Molteno Formation |
Thickness | up to 500 m (1,600 ft) |
Lithology | |
Primary | Mudstone, sandstone |
Other | Siltstone, conglomerate |
Location | |
Coordinates | 30°30′S 27°24′E / 30.5°S 27.4°E |
Approximate paleocoordinates | 44°06′S 1°54′W / 44.1°S 1.9°W |
Region | Eastern Cape, Free State, Mafeteng, Maseru, Quthing, Qacha's Nek & Mohale's Hoek |
Country | ![]() ![]() |
Type section | |
Named for | Elliot, Eastern Cape |
The Elliot Formation is a geological formation and forms part of the Stormberg Group, the uppermost geological group that comprises the greater Karoo Supergroup. Outcrops of the Elliot Formation have been found in the northern Eastern Cape, southern Free State, and in the eastern KwaZulu-Natal provinces of South Africa. Outcrops and exposures are also found in several localities in Lesotho such as Qacha's Neck, Hill Top, Quthing, and near the capital, Maseru. The Elliot Formation is further divided into the lower (LEF) and upper (UEF) Elliot formations to differentiate significant sedimentological differences between these layers. The LEF is dominantly Late Triassic (Norian-Hettangian) in age while the UEF is mainly Early Jurassic (Sinemurian-Pliensbachian) and is tentatively regarded to preserve a continental record of the Triassic-Jurassic boundary in southern Africa.[1] This geological formation is named after the town of Elliot in the Eastern Cape, and its stratotype locality is located on the Barkly Pass, 9 km north of the town.[2][3][4]
Geology
[edit]The Elliot Formation unconformably overlies the Molteno Formation and is conformably overlain by the Clarens Formation. Due to the reddish colour of the rocks, the Elliot Formation is colloquially referred to as the “Red Beds” in older geologic literature.
The Elliot Formation is dominated by mudstones and siltstones that can be finely laminated. However, the internal structures in the mudstones are often not visible due to locally poor laminations. Calcareous nodules are also found in the mudstone layers and become more frequent up section into the UEF. The mudstones range in colour from greyish purple red in the LEF and turn a more brick red colour with more mature palaeosols in the UEF. Localized intraformational pebble conglomerates that comprise intrabasinal clasts that comprise mud chips, quartzite pebbles, pedogenic nodules, and fossil bone fragments only occur in the UEF. The lower and upper Elliot formations both contain sandstones but they vary in their internal geometries. The sandstones of the LEF mainly comprise laterally accreting channel deposits that are multi-story and contain trough, low angle, and planar, cross-bedding. Ripple cross laminations with good horizontal lamination are also present. In the UEF, sandstone beds are single story and mainly reflect downstream accretion channel geometries and are more tabular in appearance. Common internal sedimentary structures of UEF sandstones are planar, low angle cross-bedding, horizontal and ripple-cross laminations.
The LEF was deposited in a fluvio-lacustrine environment where rivers were more perennial and formed meandering channel geometries, as evidenced by the presence of lateral accretion. However, this depositional environment changed at the onset of the UEF deposits where evidence of shallower river channels, longer periods of floodplain stasis (mature palaeosols) and flash flood events (pedogenic nodule conglomerates) shows that the climate became more arid.[5][6][7][8]
Correlation
[edit]The Elliot Formation is currently considered to correlate chronostratigraphically with geological formations of the Bodibeng Sandstone of the Tuli Basin in Botswana, the Omingonde Formation of the Etjo Basin in Namibia, and the Chinle Formation of the Colorado Plateau in Utah, United States.[9][10][11][12][13][14]
Paleontology
[edit]The Elliot Formation is well known for its diverse dinosaur fossils. The most common dinosaur species is of the sauropodomorph species Massospondylus carinatus.[15][16] Other species include Blikanasaurus cromptoni, Aardonyx celestae, Euskelosaurus browni, Antetonitrus ingenipes, Pulanesaura eocollum, and the largest sauropodomorph yet found, Ledumahadi mafube.[17][18][19][20][21][22][23][24] Fossilised Massospondylus eggs, some with the fossilized remains of embryos intact, have been recovered from UEF deposits in the Golden Gate Highlands National Park.[25][26] Euskelosaurus fossils are more common in the LEF while Massospondylus are only found in the UEF. The basal ornithischian dinosaurs, Heterodontosaurus tucki, Lesothosaurus diagnosticus, Abrictosaurus consors, and Lycorhinus angustidens have also been recovered from the UEF.[27][28] In addition this formation has yielded various crocodylomorph species,[29] namely Litargosuchus leptorhynchus, Sphenosuchus acutus and Orthosuchus stormbergi.[30][31][32][33] A large theropod dinosaur, Dracovenator regenti, has been found in the UEF.[34] Synapsids from the formation include the dicynodont Pentasaurus goggai[35] the tritheledontid cynodont Elliotherium kersteni[36][37] and the mammaliaform Megazostrodon rudnerae.[38] More recent vertebrate fossil finds near the town Qhemegha in the Eastern Cape have yielded possible fossil material of a poposauroid pseudosuchian. The mudstones of the LEF sometimes yield petrified wood, fossil plant matter, crustaceans, fishes, and turtles while the sandstones of the upper Elliot Formation more often contain various trace fossils. These include vertebrate trackways of basal ornithischian dinosaurs found in the Leribe, Mafeteng, and Mohales Hoek Districts of Lesotho. Possible trackways of the dicynodont Pentasaurus have been found on Morobong Hill in the Mohales Hoek District of Lesotho.[39][40][41][42]
Dinosaurs
[edit]Color key
| Notes Uncertain or tentative taxa are in small text; |
Ornithischians
[edit]Ornithischians of the Elliot Formation | |||||
---|---|---|---|---|---|
Genus | Species | Location | Stratigraphy | Notes | Images |
Abrictosaurus | A. consors |
| A heterodontosaurid, formerly species of Lycorhinus | ![]() | |
Eocursor | E. parvus |
| A basal ornithischian | ![]() | |
Fabrosaurus | F. australis |
| A basal ornithischian, nomen dubium | ||
Heterodontosaurus | H. tucki |
| A heterodontosaurid | ![]() | |
Lesothosaurus | L. diagnosticus |
| A basal neornithischian or thyreophoran, formerly species of Fabrosaurus | ![]() | |
Lycorhinus | L. angustidens |
| A heterodontosaurid | ||
Pegomastax | P. africana |
| A heterodontosaurid | ![]() |
Sauropodomorphs
[edit]Sauropodomorphs of the Elliot Formation | |||||
---|---|---|---|---|---|
Genus | Species | Location | Stratigraphy | Notes | Images |
Aardonyx | A. celestae |
| A derived sauropodomorph | ![]() | |
Antetonitrus | A. ingenipes |
| A derived sauropodomorph or basal sauropod | ![]() | |
Arcusaurus | A. pereirabdalorum |
|
| A basal sauropodomorph, known from juveniles | ![]() |
Blikanasaurus | B. cromptoni |
|
| A derived sauropodomorph or basal sauropod | |
Eucnemesaurus | E. fortis |
| A possible riojasaurid | ||
E. entaxonis | |||||
Euskelosaurus | E. browni |
| A plateosaurid, potentially dubious | ||
Gryponyx | G. africanus |
| A massospondylid, potentially dubious | ||
Ignavusaurus | I. rachelis |
| A massospondylid, known from a juvenile, potential synonym of Massospondylus | ||
Kholumolumo | K. ellenbergerorum |
| A basal sauropodiform | ||
Ledumahadi | L. mafube | A derived sauropodomorph or basal sauropod, largest in the formation | ![]() | ||
Massospondylus | M. carinatus |
| A massospondylid, most common fossil found | ![]() | |
M. kaalae |
| A massospondylid, differs from M. carinatus in cranial features | |||
Melanorosaurus | M. readi |
|
| A derived sauropodomorph | ![]() |
Meroktenos | M. thabanensis |
|
| A derived sauropodomorph, formerly a species of Melanorosaurus | ![]() |
Plateosauravus | P. cullingworthi |
| A basal sauropodomorph, formerly specimens of Euskelosaurus | ||
Pulanesaura | P. eocollum |
| A derived sauropodomorph or basal sauropod | ![]() | |
Sefapanosaurus | S. zastronensis |
| A derived sauropodomorph |
Theropods
[edit]Theropods of the Elliot Formation | |||||
---|---|---|---|---|---|
Genus | Species | Location | Stratigraphy | Notes | Images |
Dracovenator | D. regenti |
|
| A dilophosaurid | ![]() |
Megapnosaurus | M. rhodesiensis |
|
| A coelophysid |
Suchians
[edit]Crocodylomorphs
[edit]Crocodylomorphs of the Elliot Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphy | Notes | Images | |
Basutodon | B. ferox |
| A dubious suchian | |||
Litargosuchus | L. leptorhynchus |
|
| A basal crocodylomorph | ![]() | |
Orthosuchus | O. stormbergi |
| A possible protosuchid | |||
Rauisuchian |
| A indeterminate large "Rauisuchian" | ||||
Sphenosuchus | S. acutus |
| A large basal crocodylomorph |
Synapsids
[edit]Synapsids of the Elliot Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphy | Notes | Images | |
Elliotherium | E. kersteni |
| A tritheledontid cynodont | |||
Megazostrodon | M. rudnerae |
| A megazostrodontid cynodont | ![]() | ||
Pentasaurus | P. goggai |
| A stahleckeriid dicynodont | |||
Scalenodontoides | S. macrodontes |
| A very large traversodontid cynodont |
References
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{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Hancox, P. J.; Sidor, C. A. (March 2006). "Elliotherium Kersteni, A New Tritheledontid from the Lower Elliot Formation (Upper Triassic) of South Africa". Journal of Paleontology. 80 (2): 333–342. CiteSeerX 10.1.1.557.9156. doi:10.1666/0022-3360(2006)080[0333:EKANTF]2.0.CO;2. ISSN 0022-3360. S2CID 130003909.
- ^ Fernando, Abdala; Ross, Damiani; Adam, Yates; Johann, Neveling (2007). "A non-mammaliaform cynodont from the Upper Triassic of South Africa: a therapsid Lazarus taxon?". Palaeontologia Africana. ISSN 0078-8554.
- ^ E, Gow, Chris (1986-06-30). "A new skull of Megazostrodon (Mammalia, Triconodonta) from the Elliot Formation (Lower Jurassic) of Southern Africa". Palaeontologia Africana. ISSN 0078-8554.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ Anderson, J.M.; Anderson, H.M.; Cruickshank, A.R.I. (1998). "Late Triassic ecosystems of the Molteno Lower Elliot biome of southern Africa" (PDF). Palaeontology. 41 (3): 387–421.
- ^ Smith, R.; Kitching, J. (1997-06-01). "Sedimentology and vertebrate taphonomy of the Tritylodon Acme Zone: a reworked palaeosol in the Lower Jurassic Elliot Formation, Karoo Supergroup, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 131 (1–2): 29–50. Bibcode:1997PPP...131...29S. doi:10.1016/S0031-0182(96)00143-5. ISSN 0031-0182.
- ^ Knoll, Fabien (January 2005). "The tetrapod fauna of the Upper Elliot and Clarens formations in the main Karoo Basin (South Africa and Lesotho)". Bulletin de la Société Géologique de France. 176 (1): 81–91. doi:10.2113/176.1.81. ISSN 0037-9409.
- ^ Sciscio, Lara (December 2015). Position of the Triassic-Jurassic boundary in South Africa and Lesotho: a multidisciplinary approach aimed at improving the chronostratigraphy and biostratigraphy of the Elliot Formation, Stormberg Group (Thesis). University of Cape Town – via OpenUCT.